Cartilage destruction of the distal radioulnar joint is often caused by disease, such as different types of rheumatoid diseases, especially rheumatoid arthritis. Today these injuries are operated rather late in the evolution of the disease when pain evolves or mobility starts to decrease. At this time the joint most often is destroyed without remaining cartilage and with varying degrees of bone destruction. A common operation often used is the Darrach procedure, which consists of a simple resection of the ulnar head (caput ulna). The cut ulnar bone-end is now mobile and “floats” and sometimes the wrist feels unstable and painful. There is a risk for the ulna and radius to stick to each other. Sometimes the patient feels a clicking sensation, sometimes painful, when turning the forearm. Another consequence of rheumatoid arthritis is a destruction of the ligaments, joint capsule or other connective tissues stabilizers crossing the DRU joint. A tear or weakening of these structures such as the distal radioulnar ligaments and the interosseus membrane, as a result of rheumatoid diseases can compromise the stability of the DRU joint because of the loss of tension in the radioulnar ligaments. This loss of ligament tension may allow the DRU joint to sublux or dislocate.
In the non-rheumatoid patients, the DRU joint most often is injured as a consequence of a distal radial fracture and/or any distal radioulnar ligaments or interosseus membrane tear, causing a secondary joint surface incongruity or instability of the distal radial ulnar joint. The incongruity may also occur as a consequence of an intraarticular radial fracture extending into the DRU joint. The joint surface then heals with a step-off. Also a radial fracture, which does not extend into the DRU joint, might influence the congruity due to an angulation of the radial shaft and the radial joint surface of the DRU joint. A distal radioulnar ligament tear might compromise the stability of the DRU joint as a consequence of loss of tension in the radioulnar ligaments or interosseus membrane. This loss of ligament tension may allow the DRU joint to sublux or dislocate.
The consequence of an incongruity may be an osteoarthritis, which might be either symptomatic or not. Different treatment alternatives exist, none of them being particularly good. All are compromises, trading different wrist and hand functions to achieve pain relief. A common method is the Sauvee-Kapandjii procedure, where the ligaments from the ulnar tip to the radius and carpus are maintained, the ulna is resected proximally and screws keep the ulnar head to the radius. The radius together with the ulnar head now pivot within the osteotomy defect. Other known methods comprise the Bowers hemiresection of the ulnar end with soft tissue interposition and the Watson distal ulnar resection. Methods to resect the ulnar head and replace it with a prosthesis are also described; see for example, U.S. Pat. Nos. 5,951,604 and 6,302,915 and published international application No. WO 2004/071357.
U.S. Pat. No. 6,814,757 to Kopylov et al. teaches the use of implants to resurface the articular surface(s) of the distal portion(s) of radius and/or ulna bone(s) that form the DRU joint without meaningfully disturbing either the ligaments or their attachment sites that stabilize the DRU joint so as to keep the DRU joint as intact as possible.
Although the '757 patent system provides an effective treatment system, in the orthopedics industry, there is a constant search for improvement.